Knife sharpener



FIG. 1 is a side elevational view of a knife sharpener showing my new design, the opposite side being a mirror image except that it does not include an on/off switch;

FIG. 2 is a top plan view thereof;

FIG. 3 is an end elevational view thereof, the opposite end being a mirror image;

FIG. 4 is a bottom plan view thereof. 

The ornamental design for the knife sharpener, as shown and described. 